One clear message delivered by vampirism, real as well as fictional, is that the human body is a double-edged sword, both life-giving and lethal. A human being who is fully alive and animated with a soul, or one who is dead and crumbling into dust, presents no extraordinary danger. But, within the framework of the vampire tradition, anything in between—the ambiguous corpse—is to be feared. Even people who knew nothing of death-causing germs understood that, if one lost enough blood, one died. So, if blood itself is not the life, it must contain the essence, soul, or spirit of life. This concept, termed  “vitalism,” was carried well into the nineteenth century by physicians who viewed blood as the “paramount humor.” Vampires, eager to obtain this conveyer of life, sought out its nearest source—their living relatives.

The magical power of blood is one of the two fundamental principles upon which the vampire concept rests. And if life was in the blood, its home was the heart. According to European and European-derived folklore, the heart’s blood is the brightest red, which explains why the bright red blood from a consumptive’s lung hemorrhages (freshly oxygenated) was seen as blood from the heart. Beliefs concerning the restorative powers of both blood and the heart are ancient. By eating the blood or heart of a slain person, one could acquire his life, soul, courage, power, or other such qualities. In our folklore, the heart of anything is its essence, its center, its soul. Indeed, the heart was long supposed to be not only the seat of passion—and by logical extension, love and courage—but the locus of life itself. It was thus horrifyingly unnatural to discover “fresh” blood in the heart of an exhumed corpse. People understood that blood coagulates following death, but they apparently did not know that blood can liquefy again, depending on the circumstances of death. That blood in its liquid state proclaims the presence of life goes back at least to the Greek conception of life as the ongoing  reduction of liquid inside a person.  A corpse that has decomposed is dry, indicating that death is complete and the corpse is inert. But a corpse that has not sufficiently dried—one with liquid blood still in the heart, say—would be viewed as incompletely dead. The remedy was to remove life’s liquid by burning the heart or the entire corpse, thus consummating the drying process. As long as a corpse was a fountain of life, it retained the potential to be an instrument of death.

The second fundamental principle of the vampire concept, the belief in life after death, raises some fundamental questions that transcend time and place and, therefore, speak to what it is to be human: What is death? When is a person truly dead? Can the dead interact with the living? What is the relationship between the impermanent and the eternal aspects of a human being? In the early nineteenth century, a definition of death as the point at which the heart and lungs cease to function, termed the “cardiopulmonary standard,” began to displace the long-standing belief that putrefaction (or decomposition) was the decisive sign of death. The older conception persisted into the beginning of the twentieth century, however, as a number of medical practitioners continued to voice misgivings about their ability to objectively determine death. Thus, strangely, both vampire hunters and medical practitioners in pre-twentieth-century America were in agreement that putrefaction was the key for distinguishing death from life.